Magnesium deficiency and sugar transport in muscle. Effect of acute insulin deficiency.

Abstract

Intact diaphragms from magnesium (Mg) deficient rats had an increased 2-deoxyglucose (2-DG) uptake from Mg free medium. Acute insulin deficiency induced by the administration of anti-insulin serum did not inhibit transport. Addition of Mg to the incubation medium reversed the increased 2-DG transport. Transport as a function of the external 2-DG concentration conformed to Michaeles-Menten kinetics; Mg and insulin deficiency lowered the transport Km with no change in the Vmax Both saturation kinetics and competitive inhibition were demonstrated during the acceleration of sugar transport, while studies with L-glucose and L-arabinose showed no facilitation of nonspecific diffusion of sugar into muscle cells. These studies indicate that the carrier system is preserved in diaphragms from Mg and insulin deficient rats and accounts for a major portion of 2-DG transport. They also suggest that in Mg deficiency enhanced 2-DG penetration occurs both by an insulin independent and by an insulin sensitive mechanism.